Train control system



Sept. 5, 1933. A. E. HUDD TRAIN CONTROL SYSTEI Filed lay 27 1927 4Sheets-Sheet 1 Inuen ur ElleiE'P-"Z'nas Hudi Sept. 5, 1933. A. E. HUDD1,925,252

TRAIN CONTROL SYSTE Filed Ilay 27 Y 1927 4 Sheets-Sheet 2 nUEnDI" Elfrez.E1-@Huid Sept. 5, 1933. A. rs.v HUDD TRAIN CONTROL SYSTEM Filed May27., 1927 0; li'rglgrrl 4 Sheets-Sheet 3 Inval-111:1" Hlfd EWSTI'HLLEZELSept. 5, 1933. A, E, HUDD TRAIN com'noz. sYsrsu Filed May 27 1927 4Sheets-Sheet 4 [nuen nr ZfedErmHudi Al EEG Patented Sept. 5, 1933UNITEDl STAT-ES TRAIN coNTRoL SYSTEM Alfred E. Hudd, Evanston, Ill.,assignor, by mesne assignments, to Associated Electric Laboratories,Inc., Chicago, Ill., a corporation of Dela- Ware Application May 2'?,1927. Serial No. 194,587

24 Claims.

The presen-t invention relates in general to automatic train controlsystems, but is particularly concernedwith the provision of anintermittent inductive automatic trai-n stop arrangement provided withfacilities for imposing speed control features not ordinarily found inthe commonly known train stop systems. v

In all systems in this category known to applicant the engineman, ifalert, may forestall the automatic application of brakes on passing asignal at caution vor danger and after having done so, he may continueat full speed if he so desires without any further check until he comesto the next signal. signal given, either visual or audible, to remindthe engineman that he is in -or approaching a danger zone, or whether hehas or has not operated his foresta-lling device at the last signal hehas passed, or whether it was the one before the last.

Among the more important features provided for in the-present systemare: a forestalling device as in other systems; the provision of audibleand visual indications given when a signal at caution or danger is beingpassed; means for enforcing a time interval between two successiveacknowledgment operations, which enables a speed control to beestablished when approaching stop signals, and which will automaticallycause the application of brakes if the train exceeds a desired lowspeed; means for giving a clear indication upon passing a signal atclear by a positive action of the apparatus; and of a simple and ruggeddetecting device operated from the locomotive cab to enable the traincontrol apparatus to be reset to normal only when the train has come toa complete standstill.

There are other miscellaneous less important features not specificallymentioned, but which will be brought out in the specification andclaims.

The invention is herein disclosed in four sheets ci drawings; sheets l.and 2, (Figs. l and 2) should be laid out adjacent to each other withthe corresponding parts in alignment, While sheet 3 (Figs. 3 and 4)should be placed directly below sheet 2, with the corresponding parts inalignment. Sheet `4, comprising Fig. 5, discloses a diagram andassociated track circuits and is complete in itself.

Considering the iigures more in detail, Fig. 1 discloses a standardlocomotive brake valve equipped with a special operating handle and acin-operating pneumatic applicator and controlling valve.

Fig. 2 discloses a unit comprising an electro pneumatic valve EP andmiscellaneous other associated pneumatic devicessignals and airreservoirs. The major part of the apparatus is shown in section so thatthe relation between the various component parts may be more readilyshown and described.

Furthermore, there is noV Fig. 3 shows a stop detector in normalrelation to a vehicle wheel.

4 is a View of the impulse pickup relay equipment suspended from atender frame. The shown partly in cross-section as is also an associatedroadside magnet.

The various elements in Figs. l and 2 areV shown in their normalposition and it will be observed that when in this position theelectropneumatie valve EP is energized over a circuit extending from abattery, through the winding` of the EP valve magnet, conductor 48,contacts 21 of the pickup relay, conductor 48', and through the detectorrod and associated conductor to ground. With the EP valve energizedvalve 6 is held closed. Under these circumstances the air chamber A ofFig. l and the communicating pipe 3 connecting it with the reservoir i3oi Fig. 2 and the reservoir itself are under full air pressure from themain reservoir (not shown) supplying air to them via needle valve 4.With this state of affairs existing, the main reservoir pressure inchamber A is ample to hold the valve 10 seated'.

The other valves 26, I9 and 28 are normally held in the positions inwhich they are shown, by air pressure normally applied to the respectiveair chambers 15, i6, and D. The contacts t8.y are also normallymaintained closed, as shown, by air pressure on the diaphragm 31.

Fig. E discloses a stop detector SD in operative relation with alocomotive wheel and which is a pneumatically operated device of thetype shown and described in detail in the copending Hudd application,Serial Number 170,048, filed Feb. 21st, i927. This device consists of apneumatically operable plunger carrying a spherical valve adapted to beopened only when the element 46 is forced into engagement with the wheelwhile' the wheel is moving, as. described in detail in the applicationreferred to.

Fig. Ll shows a permanent magnet "roadside inductor and a receiver orpick up relay. The structure of the electromagnet inductors are alongthe same general lines. The structure of the pickup relay is similar toa relay used for the samepurpose in the system disclosed in a co-pendingHudd application bearing Serial No. 139,794, filed Oct. 6, 1926, but theoperating and restoring circuits are slightly different. This pickuprelay like the one in the former disclosure has a permanent magnet whichholds the armature biased to either position to' which it is operated.The relay and its associatedpick-up brushes are suspended from thetender frame by a number of bolts, two of which can be seen in thisligure. It will be observed that a third bolt labeled detector rod isused as a conductive element through which current is supplied to a pairof reset coils 39 of the pick-up relay 'CII and to the EP valve magnet.These reset coils are energized under certain conditions to restore thearmature of the pickup relay, as will be described subsequently. Thedetector rod is turned out of cast iron and, therefore, is very brittle.Should the pick-up relay or the associated structure come info contactwith anything with sufficient force to bend the supporting bolts orother- Wise render the equipment useless, the impact will be sufficientto break the relatively brittle detector rod and bring about thedeenergization of the electropneumatic valve EP. This will cause anautomatic brake application to occur in a manner which will besubsequently made clear.

Fig. 5 shows a diagram illustrating a trackway divided up into a numberof blocks or sections with associated block signals at clear, caution,stop, and clear, positions respectively. The brake control curve whichshould be followed under the conditions indicated is also shown, as arealso track circuits for determining the condition of the roadsideinductors.

Before going into the description of the various cycles of operation ithas been deemed advisable to describe the track circuits and to explainhow they accomplish the Various circuit changes to vary the magneticconditions of the roadside inductors, as required to obtain the desiredtrain controlling operations.

In the illustration given a locomotive is shown travelling towards theright and is in the last complete block section shown. Under theseconditions the current normally supplied through the contacts of thethree position polarized relay 54 is shunted from the three positionpolarized relay 53, causing this relay to assume its neutral position.With the relay 53 in neutral position an operating circuit for the threeposition relay 52 is completed, from the battery associated with relay53, causing this relay to assume its neutral tures of this relay, thelower track rail, the winding of the three position polarized relay 52,and the upper track rail back to the opposite side of the battery. Thecurrent flow to the relay 52 is in the appropriate direction to causethis relay to rotate its armatures in a counter-clockwise direction,into the position in which they are shown.

With the relay 52 in this position a circuit through the distantassociated electromagnet trackway element is completed, which extendsfrom the battery associated with the relay 52 to the armatures and lowercontacts of this relay, through the distant electromagnet, the lowertrack rail, through the polarized relay 51, and back to the battery overthe upper track rail. The current flow is in the appropriate directionto cause the armatures of the relay 51 to be rotated in a clockwisedirection into engagement with their upper contacts.

With the relay 51 in this position it supplies current from the batteryat this point, through its armatures and upper contacts, to theassociated distant and home electromagnet trackway elements in multiple,and to the lower trackway rail. At the entrance of this block is anotherthree position relay, not shown, through which the battery current flowsto the upper trackway rail and back to the other terminal of thebattery.

Upon reviewing the trackway circuits, just traced, it will be noted thatthe roadside inductors, both distant and home, of the blocks havingtheir semaphores in clear position are enerj gized; only the distantroadside inductor of the block having its signal at caution isenergized;

while neither the distant or home roadside inductor associated with theblock having its signal at stop is energized. The coordinate control ofthe semaphore blades may be of any customary type, and does not form apart of applicants invention,

With these facts in mind we will now divert our attention to the variouscycles of operation which take place as the locomotive passes over thevarious sections when track conditions are as indicated in Fig. 5.

Passing a signal at clear As shown by the circuit of the diagramdisclosed in Fig. 5, on passing a signal at clear the receiver on thelocomotive rst passes over a permanent magnet, which deflects thereceiver armature 45 and breaks contacts 21, opening the normallyestablished circuit for the electropneumatic valve EP. Theelectropneumatic valve, upon becoming deenergized drops its armature 29permitting the associated valve 6 to open. This allows the pressure inchamber A and reser voir B to be reduced, as the openings thru valve 6and chamber E are very large compared to the air supply thru needlevalve 4. After approximately 6 feet of travel, the locomotive receiverpasses over the associated electro-magnet roadside inductor which, dueto the circuit condition indicated in Fig. 5, resets the armature 45,again closing contacts 21, so that the electropneumatic valve againbecomes energized, closing valve 6, and thus restoring the operatedapparatus to its original condition. The armature 29, in dropping, also,through the medium of the spring 23, permits spring 22 to break thecircuit of the green lamp G and close the circuit of the red lamp R. Thegreen lamp will therefore be momentarily extinguished and the red lampwill be lighted during the brief period during which theelectropneumatic valve is deenergized. This momentary signal changeserves to indicate to the en-r gineer that he passed a trackway deviceat clear.

The foregoing operations take place at all clear signals and constitutea self checking or positive action and, unless the train is running atvery low speed, the whistle W will 'not be sounded, for the reason thatit takes one half second for the chamber E behind the whistle to fill upbefore the whistle can blow. This arrangement avoids calling theenginemens attention audibly when passing a signal at clear.

Passing a signal at caution Referring again to the diagram of Fig. 5, itwill be seen that a pair of roadside magnets is located 500 feet behindeach signal location andV that, in addition, there is a pair of magnetsxed at the signal itself.

As clearly indicated in the circuit and as previously traced, when asignal at clear is encountered both electromagnets are energized and theapparatus on the locomotive accordingly again functions as heretoforedescribed, when passing the pair at the signal itself, but when thesignal is at caution the second electromagnet encountered isdeenergized, as indicated; therefore, the electropneumatic valve EP isnot restored at the second electromagnet. The deenergizedelectropneumatic valve, at its contacts 24, opens the normally closedcircuit of the green lamp G and at its contacts 25 closes the circuitfor the red lamp R. Since on this occasion the reservoir pressure inchamber B is being reduced for a period greater than one half second,the air pressure in chamber E rises suiiciently to cause the whistle Wto blow and give the enginemen a further warning of the condition underwhich he is operating the locomotive. Acknowledgment must be made atthis time by the engineman who must hoid the acknowledging plunger AP inoperated position until the whistle stops blowing in order to avoid anautomatic application o the brakes. When the acknowledging plunger AP isoperated it opens valve 26 which connects chamber 16 with atmosphere andalso the chamber l5 immediately above valve diaphragm 27. The smallorifice 17 thru which the main reservoir pressure is being supplied isnot suiiicient to maintain the pressure on top of diaphragm 27 and,therefore, the Valve 28 becomes released. This permits a momentary rushof air from the valve chamber D to pass out thru the pipe 14 onto thedisk 15', raising the spring 29 suiiiciently to momentarily closecontacts 13. This results in a circuit being established from a battery,through contacts 38, conductor 30, thru contacts 13. conductor 34, andthe windings of reset coils 39, and the detector rod to ground. Thereceiver armature consequently becomes restored to its normal conditionand reestablishes the hereinbefore traced circuit of the EP valvemagnet.

It will be noted that the movement ol" the acknowledging plunger LPpushes the spring 23 out of engagement with contact spring 22 and thatit is held out oi range of spring 22 until armature 29 has been restoredto its normal energized condition. The result is that when spring 23 isreturned to its normal height by the electropneumatic valve armature thespring 22 remains in engagement with its lower Contact and, therefore,the red light is not changed and remains in a lighted condition untilthe armature 29 has fallen and picked up again with the plunger .APreleased. Only under this condition is the spring 23 permitted to catchthe underside of spring 22 and so raise it to its normal position,opening contacts 25 and closing contacts 24.

Since it is only when signals at clear are encountered that theelectropneumatic valve EP is deenergized and restored again without theaid of the acknowledging plunger, it follows that the green light canonly be restored on passing a signal at "clear-2 Returning to the actionof contacts 13, it will be noted that the chamber D is of very lowcapacity and therefore allows air o sufiicient pra sure to actuatecontacts 13 only for a very short duration of time, the opening 18 tothe main reservoir being reduced suiciently to prevent anyT rise ofpressure in the chamber D when valve 28 is open. For this reason it willbe seen that only a momentary closing of contacts 13 can be accomplishedat the iirst'inward movement of the plunger AP.

When the plunger is rst operated the chamber D is discharged as is alsothe reservoir C and the space on top of diaphragm 27. The orice 17 tothe main reservoir and the size of the reservoir C are so adjusted thatafter one actuation of the plunger AP sufficient air pressure cannot beagain applied to diaphragm 27 to close valve 28 until chamber C has beenrecharged. This requires approximately 20 seconds. It follows that asecond blast of air cannot be given to close con-V tacts 13 until thatamount of delay has taken place.

usual way after passing the iirst encountered pair of magnets, but whenthe train reaches the signal another impulse is received and againdemands acknowledgment.

1f twenty seconds had expired since the rst acknowledgment vwas made,the average speed between the two pairs of inductors was approximatelytwenty iniles per hour; accordingly a second acknowledgment can be madein the same manner as was the first. However, if the engineman hasdisobeyed the previous warning and maintained an average speed of overtwenty miles per hour he will arrive at the second acknowledgM ing pointbefore the required laps of 2O seconds and an operation of theacknowledging plunger will be without ei'ect. Consequently, due to thecapacity of reservoir B and adjustment of needle valve 4, within sixseconds after encountering the -ermanent magnet at the signal, the airpressure in the line 3 will have been reduced to ten pounds which asufficient reduction to permit the main reservoir pressure to overcomethe pressure on piston 8 and piston 11 will be actuated to apply thebrakes.

The automatic application of the brakes An automatic brake applicationhaving once been initiated, either by failure to acknowledge a cautionor danger signal, or by having eX- ceeded the speed limit on approachinga stop signal, cannot be annulled until `the train has come to a standstill. The provision made for this control comprises the pneumaticswitch PS, having its contacts 38 normally closed by air pressureapplied to its diaphragm 31. The spring 32 is so tensioned that thisswitch will open when the pressure in the line is reduced to ten poundsat which time, it will be recalled, the piston 8 in the applicatorreleases valve 10 and which is at the stage that the brakes will beautomatically applied and the circuit of reset coils 39 broken. Aspreviously described the operation of the acknowledging plunger opensthe valve 2S, so that the pressure in the chamber D is released. Therelease of pressure in chamber D in turn releases the diaphragm 33 andvalve 19. With the valve 19 released the admission of main reservoirair.

via the opening 20 will eventually close the stop detector contacts 40,provided that the locomotive is at a complete stand still. This actiontakes place although the piston 41 of this pneumatic switch normallykeeps the contacts 40 open by means of the spring 43. The area of piston41 and the strength of spring 43 are arranged so that it requires apressure of at least 70 pounds tacts 40, all as fully described in theco-pending application formerly referred to. The closing of thesecontacts completes a circuit for energizing the reset coils 39independently of the contacts 38. This circuit may be traced from abattery, through contacts 40, conductor 34 to the reset coils 30 andground via the detector rod. As soon as this circuit is closed armature45 assumes its normal position and the electropneumatic valve isenergized over a circuit extending from a battery, thru theelectropneumatic valve conductor 48, contacts 21 of the receiver magnet,and the detector rod to ground. The electropneumatic valve therefore isactuated to again close valve 6. Soon thereafter the pressure in line 3becomes sufficient to restore the piston 8 to its initial position. Inthis position the air supply to piston 1l is cut oir and the enginemancan then release the brakes by manually restoring the handle to runningposition.

Should the engineman attempt to operate the acknowledging plunger Whilethe train is in motion to effect a release, the valve element 46 willtilt over immediately it touches the Wheel and release the pressurebeing applied to the stop detector and to the piston 38, so that it isimpossible to close contacts While the locomotive is in motion.

What is claimed is:

1. In an automatic train stop mechanism, an electropneumatic valve, acircuit for normally maintaining said valve energized, a paii` ofsignals, circuits for energizing said signals including a contactoperated by said electropneumatic valve, and means for at timespreventing the actuation of said valve from operating said contact.

2. In a train control system, a normally ener-- gized electropneumaticbrake controlling valve eiective When released to cause a brake applyingaction to be initiated, signalling means also responsive to such releaseto give a Warning that the brake applying function has been initiated,means for restoring the electropneumatic valve to its energizedcondition to prevent the brakes being applied, and other meanscontrolled by said restoring means for preventing the restoration of theelectropneumatic valve from changing the responsive condition of thesignalling means.

3. In a train control system, a normally energized magnet, means forcausing the deenergization of said magnet, means operated responsive tosuch deenergization to Warn an engineman visually and audibly of thechanged condition of the magnet, means controlled by the engineman forcausing the reenergization of said magnet, and auxiliary means alsooperated incidental to the actuation necessary to reenergize said magnetfor preventing its reenergization from eX- tinguishing said visualsignal means.

4. In a train control system, an inductive pickup device, means forsupporting said device on a vehicle, a brake valve control circuitpassing thru contacts of said pick-up device normally held closed toprevent a brake application, and a brittle conductor included in saidcircuit and in the structure connecting the pick-up device With thevehicle,

5. In a train control system, an electropneumatic valve, a normallyclosed operating circuit for said valve, a train carried relay havingcontacts thru which. said circuit passes, track-Way elements foroperating said relay to cause the same to open and close said circuit,visual means for immediately Warning an engineman when the circuit isbroken, time controlled means for further warning the engineman after acertain period of time, manually operable means whereby the engineman,if alert, can cause the relay to again close said circuit, brakeapplying means effective if the engineman fails to operate said manuallyoperable means and means for preventing the engineman from effectingsaid circuit closure after the brakes have been applied until the trainhas come to an absolute stop.

6. In a train control system, an electropneumatic valve, a circuit formaintaining said valve closed, means for breaking said circuit, meansoperative consequent to the deenergization of said valve to give asignal to this effect, a reservoir and an associated needle valve thruwhich compressed air is supplied, and a second signal operated bycompressed air after the valve has remained deenergized an intervaldetermined by the capacity of said reservoir and adjustment of saidneedle valve.

'7. In a train control system, a pneumatic brake applicator, a valvenormally closed to prevent main reservoir pressure being applied to saidapplicator, means i'or normally maintaining said valve closed comprisingan air line also connected with main reservoir pressure via a needlevalve and an electromagnetically closed valve to atmosphere, means foropening said last valve to permit the nrst valve to open after the airpressure in said line has been reduced to a speciiic point, and anauxiliary reservoir also connected to said line and cc-operating Withsaid needle valve to delay the reduction of pressure in said line.

8. Tn a train control system, an electropneumatic valve, a circuitnormally maintaining said valve closed to prevent a brake application,an electrical device energized by an impulse transmitted to it from asource exterior to the vehicle to open said circuit, means for delayingthe brake application taking place for a predetermined period of time,after the circuit is opened, and a manually operable acknowledging leveroperated to cause the reclosure of said circuit before the expiration ofsaid predetermined period of time and operable to cause the closure ofsaid circuit after the predetermined period has expired only if thetrain has come to a complete stop.

9. In a train control system applied to a railway system having itstrackway divided into blocks, a pair of cab carried signals, a magnetfor actuating said signals at the exit of a block when the trafficconditions ahead are unfavorable, manually controlled means operable toretire only one oi said signals, and means for temporarily preventingthe retiring of said one signal after the expiration of a deniteinterval of time following the first change.

10. In a train control system, a vehicle carried relay, trackway meansfor inductively transmitting impulses to said relay to cause it tooperate, an electroinagnet included in a circuit controlled by saidrelay, visual and audible signals actuated by said electromagnet whenthe train is about to enter caution territory, manually operablecknowledging means for energizing said magnet to stop the actuation ofsaid audible signal, and means operable only when. the territory aboutto be entered is clear for retiring the visual signal.

11. In a train control system, vehicle carried visual and audiblesignals together with apparatus for controlling the brakes of thevehicle, pairs of trackway magnets spaced at points along the trackwayfor transmitting controlling iniiuences from the trackway to thevehicle, a relay carried by the vehicle responsive to said iniluences tovariably change the condition of said signals and to initiate theoperation of said brake controlling apparatus and manually controlledmeans operative to iniluence said relay and apparatus to change thecondition of only one oi said signals and for preventing a brakeapplication occurring under certain conditions.

l2. In a train control system, an inductive pickup relay, means orsecuring said relay to a vehicle, a brake valve control circuit passingthrough contacts of said relay normally and held closed to prevent abrake application, and means included in said securing means forinterrupting said circuit in case the relay is moved any appreciabledistance with respect to the securing means.

1S. In a train control system, an impulse receiving device suspendedfrom vehicle in a denite relation thereto, and circuit for said deviceincluding a brittle conductor extending between said receiving deviceand the vehicle which will be severed if relative movement between thevehicle and receiving device occurs.

14. In a train control system the intermittent inductive type, cabsignals, associated means for causing one of said signals to be electivewhen the vehicle is in clear territory and for automatically causinganother of said signals to be effective upon the vehicle enteringcaution territory, means for initiating an automatic brake applicationcoincident with the actuation of the last mentioned signal, a manuallycontrolled pneumatic contacter actuated to forestall the initiated brakeapplication, and means ior maintain ig a third of said signals effectiveafter the orestalling action has occurred..

l5. In a train control system, an electropneumatic valve, a normallyclosed operating Acircuit for said valve, a train carried relay havingcontacts through which said circuit passes, trackway elements foroperating said relay to cause the same to open and close said circuit,means for immediately warning an engineman when the circuit is broken,means for further warning the engineman, manually operable means wherebythe engineman, ii alert, can cause the relay to again close saidcircuit, brake applying means effective if the engineman fails tooperate said manually operable means, and means for preventing theengineman from effecting said circuit closure alter the bra-kes havebeen applied until the train has come to an absolute stop.

16. In a train control system, a pair of pneumatically operablecontacts, means operable during the progress of a vehicle ior only attimes causing a momentary actuation of said contacts, and otherpneumatically operative contacts under the control of said rst meanspermitting a closure of said last contacts only after the vehicle hasbeen brought to a standstill.

17. In a train stop system, a set or" pneumatically actuated contacts, asecond set of contacts, a control circuit including said contacts setsand Linder control of said second contact set while the rst set is inactuated position, and a third set of contacts included in a branch ofsaid control circuit under control of said second set when the rstcontact set is not actuated.

18. In a train control system, means responsive to trackway conditionsto be changed from normal to operated position, brake applying meansinitiated upon operation of said responsive means, and a plurality oiseparate, manually controllable, pneumatic reset means foreach movingthe responsive means from its operated, to its normal position.

19. In a train control system, car-carried apparatus, including a singlemeans responsive to trackway conditions, train control means controlledby said responsive means, and a plurality of manually controlledpneumatic reset means for restoring the responsive means after itsoperation in accordance with trackway conditions.

2G. In a train control system, car-carried apparatus, including, a pairof pole-pieces having an armature associated therewith, movable from oneof its pole-pieces responsive to trackway conditions, train-controlmeans controlled by said armature; reset means, separate from thatemployed to iniiuence said pole-pieces responsive to trackwayconditions, for restoring said armature; and a plurality oi separatemanually controlled means for causing said reset means to function.

21. In a train control system, brake applying means, a normally inactivemember operable in accordance with traffic conditions to causeinitiation or" said brake applying means, a restoring member arranged tobe physically moved by iluid pressure, a fluid pressure timingreservoir, and a manually operable member operable to cause fluidpressure in the reservoir to communicate with, and thereby move, therestoring member to a position to cause said normally inactive member toresume its inactive condition.

22. In a train control apparatus, the combination with a magnet valvedevice operative to cause an automatic application of the brakes, ofelectro-pneumatic means operative to control the operation of saidmagnet valve device for governing the release oi the brakes, and meanscooperating wit'n said electro-pneumatic means and adapted to timeoperation of said electro-pneumatic means.

23. In a train control system of the intermittent inductive type appliedto a railway system wherein the trackway is dividedup into blocks, apair of cab carried signals, means effective at the exit of each blockfor causing both signals or said pair to be actuated under certaintraflic conditions ahead, manually controlled means for causing theoperation of one signal of said pair to cease, and means influenced bysaid manually controlled means for causing the operation of the othersignal of said pair to continue While the train proceeds through themajor portion of the next block.

24. In a train control system, a normally energized electro-pneumaticvalve for normally preventing an automatic brake application occurring,means for causing the magnet of such valve to become deenergized, meansfor delaying a brake application occurring for a definite interval afterthe deenergization of such magnet occurs, and a cab carried readilyaccessible manually operable element having pneumatic equipmentcontrolled thereby to bring about the reenergization of the magnet ofsaid valve only if operated before said predetermined interval hasexpired, or after the vehicle has been brought to a standstill. Y

ALFRED E. HUDD.

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